# CVE-2026-102408 — Elastic Elasticsearch

> As of 2026-10-06, CVE-2026-102408 is a MEDIUM-severity vulnerability in Elastic Elasticsearch, CVSS v3.1 4.3, EPSS 0.3% (25.3th percentile). Threadlinqs Intelligence links 1 tracked threat campaign to CVE-2026-102408, most recently “Elastic Patches 14 Security Flaws Including Kibana Cross-Tenant Data Interception (CVE-2026-102406)”.

**Last updated:** 2026-10-06

## What is CVE-2026-102408?

Inefficient Regular Expression Complexity (CWE-1333) in Elasticsearch can lead to denial of service via Regular Expression Exponential Blowup (CAPEC-492). The ES|QL CHUNK function's recursive chunking strategy accepts a list of user-supplied regular expressions used as text-splitting separators, without validating their computational complexity or bounding their execution time. An authenticated user with read access to any text-based index can submit a specially crafted regular expression that triggers catastrophic backtracking, consuming excessive CPU on Elasticsearch worker threads and degrading query throughput for other tenants on the affected node. The cluster does not crash as a result of this issue.

The record classifies CVE-2026-102408 under weakness class [CWE-1333](https://cwe.mitre.org/data/definitions/1333.html). Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs low-privilege credentials, needs no user interaction. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 4 days ago.

## Severity and exploitation probability

- **CVSS v3.1 base score:** 4.3 — MEDIUM (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L`)
- **EPSS (FIRST):** 0.3% probability of exploitation in the next 30 days, higher than 25.3% of all scored CVEs
- **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog
- **Threadlinqs priority:** 3.2/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- **Published:** 2026-10-06

## Is CVE-2026-102408 being exploited?

It currently carries a trending score of 40 in the Threadlinqs vulnerability feed.

## Affected products and versions

- [Elastic](https://intel.threadlinqs.com/vendors/elastic): Elasticsearch

## How to fix CVE-2026-102408

No vendor patch reference has been recorded for CVE-2026-102408 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.

## Threat activity tracking CVE-2026-102408

1 tracked threat in the Threadlinqs corpus references CVE-2026-102408, either in the campaign’s CVE list or as an indicator on the campaign record.

- [Elastic Patches 14 Security Flaws Including Kibana Cross-Tenant Data Interception (CVE-2026-102406)](https://intel.threadlinqs.com/threat/TL-2026-3268) — HIGH · 2026-10-10

## Sources

Enriched from CVE.org, FIRST EPSS, GitHub Security Advisories. Last verified by Threadlinqs on 2026-10-10.

**Other references**

- [discuss.elastic.co](https://discuss.elastic.co/t/elasticsearch-8-19-22-9-4-8-and-9-5-5-security-update-esa-2026-189/390862)

Canonical: https://intel.threadlinqs.com/cve/CVE-2026-102408
Full detection coverage and IOCs for threats exploiting CVE-2026-102408 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp